This invention relates to handle operators which provide an interface and additional electrical isolation between the handle of a circuit breaker mounted in a cabinet behind a panel door and the person operating the circuit breaker. It also relates to such a handle operator, positioned remotely from the circuit breaker, which converts the rotary motion of the handle operator to the linear motion needed to control the pivot handle of the circuit breaker and which is further lockable in the circuit breaker off position.
A common type of circuit breaker has a pivot handle which moves linearly between an on and an off position. The pivot handle is connected to the movable contacts within the circuit breaker assembly through a spring powered, over center toggle device. When the handle is moved into the on position, the movable contacts close upon themselves creating an electrical connection. When the handle is moved into the off position, the movable contacts separate from each other interrupting the electrical connection. In response to certain overcurrent conditions, the contacts open automatically causing the handle to move to an intermediate position.
In some installations, the circuit breakers are mounted behind a door in a cabinet. Typically in these installations, the pivot handles of the circuit breakers protrude through openings in the door where they are operated directly. This configuration has the disadvantage of leaving the circuit breakers exposed to the environment. In some applications, it is deemed desirable to provide an interface between the handle and the person operating the breaker. This interface often is a flange-mounted, linearly movable, pivot handle operator. Typically, these pivoted handle operators are spring biased, usually in the off position, with the spring serving as the driving connection between the circuit breaker handle and the remote pivot handle operator.
Performance of these interfaces has not always been satisfactory. Typically, they have substantial mass which loads the over center toggle device of the breaker. The spring force of the toggle device is generally weakest at the trip position, and the additional loading imposed by the pivoted handle operator structure has made it difficult to position the handle at the trip position should a trip condition occur. While tripping of the circuit breaker is not adversely affected, accurate positioning of the handle is necessary to provide a visual indication of the tripped condition of the circuit breaker.
Another problem can arise when the known remote handle operator mechanism is locked in the off position. In some instances, this locking can be done even though the contacts within the circuit breaker have become welded closed. While this condition was made possible by the internal structure of some circuit breakers, such breakers have in many instances been modified to prevent even moving the circuit breaker to the off position when the contacts are welded closed. Despite these modifications, the known handle operator mechanisms can still be moved to and locked in the off position providing a false indication of the state of the circuit breaker when the contacts are welded shut. This is owing to the spring connecting the handle operator and the circuit breaker handle.
There exists a need for an improved remote circuit breaker handle operator for use in flange-mounting. It is also desirable to replace the remote, linearly movable, pivot handle operator with a remote, rotatable handle operator. More particularly, a need has been shown for an improved handle operator which does not place a load upon the spring of the toggle device and which further operates without a biasing spring connection. This improved handle operator should have the capability of being locked in the off position without misrepresenting the state of the circuit breaker, should provide the circuit breaker mounted in the cabinet an environment sealed from dust and moisture, should incorporate an interlock for the door of the cabinet in which the circuit breaker is mounted, and should have its coupling free from the problems of sagging, misalignment, and preventing proper door closure.